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  • 1
    ISSN: 1432-1106
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Factor H is a major regulatory protein of the complement system. The complete cDNA coding sequence has been derived from overlapping clones, and a polymorphism at base 1277 has been characterized. In four clones there is a T at nucleotide 1277 and in two others there is a C. This T/C change represents a tyrosine/histidine polymorphism at position 384 in the derived amino acid sequence. Protein sequence studies on peptides generated by trypsin digestion of factor H, purified from pooled plasma from 12 donors, confirmed the presence of both tyrosine and histidine at this position. Tyrosine and histidine were observed in a ratio of 2 : 1, respectively, and therefore this polymorphism is likely to represent a sequence difference between the two most abundant charge variants, FH1 and FH2, of factor H.
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  • 3
    ISSN: 1432-1106
    Keywords: Rat ; Lateral geniculate nucleus ; Thalamic reticular nucleus ; Bursts ; Inhibition ; Receptive fields
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Two-shock inhibition, a feature of 98 of 100 P cells recorded in the dorsal lateral geniculate nucleus of the normal rat, was not observed in 91 of 140 geniculate cells after an electrolytic lesion had been made in the adjacent visually responsive thalamic reticular nucleus. Nine geniculate cells recorded both before and after a reticular lesion had their initial inhibition abolished or substantially reduced after the lesion. The reticular lesion eliminated the bursts of spikes which normally terminate periods of inhibition following electrical or photic stimulation but caused no other changes in receptive field organization of geniculate cells. We conclude that the visually responsive region of the thalamic reticular nucleus in the rat is responsible for the profound two-shock inhibition and for the post-inhibitory bursts which are normal properties of relay cells of the dorsal lateral geniculate nucleus.
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  • 4
    ISSN: 1432-1106
    Keywords: Neurogenesis ; Neural development ; Olfactory receptor cell ; Tiger salamander
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The factors controlling neurogenesis and differentiation of olfactory receptor cells in adults are poorly understood, although it is often stated that these cells undergo continual turnover after a pre-determined lifespan. An interesting model in which to study mechanisms which control olfactory receptor neurogenesis and cell turnover is the tiger salamander, since basal cell mitosis varies with epithelial thickness and location in the nasal cavity. This paper presents a quantitative light-microscopic study of the different cell types within the ventral olfactory epithelium of the tiger salamander using a computer-assisted morphometric analysis of 2 μm sections. The results show that the surface density of olfactory vesicles remained constant throughout most of the epithelium and was independent of nasal cavity location, epithelial thickness and the total number of nuclei per unit epithelial surface area. Histological classification of nuclei into different cell types indicated that the increase in total cell number with epithelial thickness was mainly due to an increase in the number of immature receptor cells since the number of supporting cells varied only slightly and the numbers of basal cells and mature receptor cells remained constant except in the thinnest, most caudally located epithelium. It is concluded that the rate of maturation of receptor cells may be limited by an optimal surface density of olfactory vesicles. That is, when this density reaches 4.5×104 vesicles per mm2 there is a physical or chemical mechanism which prevents the final maturation of newly developing receptor cells, leading to their accumulation. This mechanism may also account for the variations in basal cell mitosis in this species.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 76 (1989), S. 207-212 
    ISSN: 1432-1106
    Keywords: Zinc deficiency ; Olfactory epithelium ; Sense of smell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Adult zinc deficiency reportedly leads to degeneration of the olfactory epithelium in the rat. Human zinc deficiency can cause reduced olfactory sensitivity. Given the importance of zinc in embryonic neural development its primary action on the adult olfactory system may be to disrupt olfactory receptor neurogenesis. We report here on the effects of zinc deficiency on the olfactory system of the adult mouse. After 42 days of dietary restriction of zinc, mice were tested behaviourally for olfactory function and general activity. Their olfactory epithelia were examined histologically using [3H]-thymidine autoradiography to identify recently-divided cells, and immunohistochemistry for olfactory marker protein to identify mature receptor neurones. Zinc deficient mice failed to show a food odour preference but they Were as active as controls and their olfactory epithelia appeared normal. Basal cell proliferation and postmitotic survival were similar to controls and the epithelia were of normal thickness and were positive for olfactory marker protein. It was concluded that zinc deficiency did not affect the turnover of cells in the olfactory epithelium. It may disrupt olfactory function through interference with zinc-containing neurones in higher olfactory centres.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Skeletal radiology 15 (1986), S. 77-81 
    ISSN: 1432-2161
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. The inhibitory effect of morphine, nalorphine, oxymorphone, naloxone, naltrexone, N-methylnaloxone, levorphanol, levallophan, dextrorphan, dextrallophan, levo-methadone, dextro-methadone, pethidine, leu-enkephalin and U-50 488 on the acetylcholine (ACh)-induced contraction of the toad rectus was investigated.2. The dose-response curves obtained in the absence and presence of increasing concentrations (0.1–3.2 or 10–320 μmol/l) of each opioid were subjected to three types of inhibition model discrimination, namely competitive, noncompetitive and uncompetitive.3. The results show that the opioids, except morphine, nalorphine and levorphanol, inhibit the ACh-induced contraction by multiple modes of action. Except for the morphinans, the opioids inhibit competitively indicating that they are able to compete with ACh for cholinergic receptors at the nicotinic site.4. The opioids also inhibit noncompetitively (except oxymorphone and N-methylnaloxone) and uncompetitively (except oxymorphone) indicating the possible existence of separate opioid binding sites and the combination of the opioids with the ACh receptor complex, respectively.5. The effect of morphine and levorphanol on the ACh-induced contraction varies with the concentration of the two opioids. At concentrations below 80 μmol/l both opioids tend to inhibit the contraction while at concentrations of 80 μmol/l and above there is no apparent effect. Nalorphine has no effect on the contraction at the concentrations (10–320 μmol/l) employed in the study.6. An apparent structure-activity relationship between the phenanthrenes and the various binding sites is noticeable; so also is the difference in the activity between the dextro and levo-isomers of levorphanol and levallorphan indicating that the receptors exhibit stereospecificity.
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  • 8
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. Intracerebroventricular captopril produces significantly different effects on the sleep electroencephalogram (EEG) of normotensive Wistar-Kyoto (WK) and spontaneously hypertensive rats (SHR).2. The compound produces a definite pattern of decrease in the percentage and power of the lower frequency EEG of the SHR. Corresponding action on the WK was confined to a general decrease in the power of the EEG.3. These findings suggest that certain components of the central renin-angiotensin system in the SHR are abnormal.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. The anti-acetylcholinesterase (AChEase) activity of 15 opioids, namely morphine, nalorphine, oxymorphone, naloxone, naltrexone, N-methylnaloxone, levorphanol, levallophan, dextrorphan, dextrallophan, levo-methadone, dextro-methadone, pethidine, leu-enkephalin and U-50,488H was investigated.2. Among the opioids, the morphinans (in terms of their dissociation constants) are the strongest inhibitors of the enzyme. These are followed by the phenanthrenes and the morphones, though two members of the latter group are non-inhibitors. Levo-methadone, dextro-methadone, pethidine and leu-enkephalin are also non-inhibitors of the enzyme.3. The present results, together with our previous findings, support the suggestion that opioids which are poor or non-inhibitors of AChEase are strong inhibitors of the ACh-induced contraction of the toad rectus, whereas the reverse is true for inhibitors of AChEase.
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  • 10
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. Certain commercial preparations of oxytocin have been reported to reverse the development of pale soft exudative meat and malignant hyperpyrexia (MH) in pigs in vitro.2. In this study it is shown that preservative-free oxytocin has no significant effect on the characteristic contractures of MH susceptible (MHS) muscle to halothane, caffeine, succinylcholine and KCl in vitro.3. Whilst a commercial preparation of oxytocin, Syntocinon (containing chlorbutol as preservative), reversed and prevented the MHS characteristic responses, this study demonstrates conclusively that this was entirely due to the preservative chlorbutol.
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